The Weakest Creatures In The Oceans: Humans.

There are a multitude of extreme marine environments that exist across the world, whether it be the dark depths of the oceans or the ice cold waters of the Antarctic. In each of these environments, hundreds of species of animals exist, perfectly adapted to not only survive, but thrive. What happens if we take a look closer to home though? Each year, hundreds of thousands of people take vacations to beach side resorts and and hundreds of thousands of people live around rivers, lakes, and oceans. In fact, primitive people even seeked out these locations for survival – water offers the opportunity of life to plants, animals, and humans alike. This begs the question of why do we flock to these watery locations if we’re so ill equipped to survive in the water?

The issue with animals

The first way that humans show their ineptness at surviving in water is how easily they are attacked. Shark attacks have been the focus of books, tv shows, movies, and news articles for years. The media has affected the world’s outlook on sharks from an early time, which was thought to begin with the attention the “Jersey Shore shark attacks of 1916” gained, where four people were killed in the first two weeks of July 1916. Since the release of world famous book “Jaws” by Peter Benchley, sharks have become stigmatised and scare many people from the idea of going into the water. The chances of encountering a shark in the oceans of the world are only increasing now that the average temperature of the world’s oceans is increasing. The west coast of Australia, South Africa, and Florida are considered to be “shark attack hotspots” due to their number of attacks per year and their access to warm, open waters. There are around 80 shark attacks against humans every year, which is a very low amount considering the amount of people in the water every year. There are three shark species that have double digit fatality rates; Great White Shark (Carcharodon carcharias), Tiger Shark (Galeocerdo cuvier), and Bull Shark (Carcharhinus leucas). In 2016, there were four recorded fatalities worldwide, which was lower than the 2011-2015 average of eight fatalities. Even lower is the chance of being killed by a shark attack, which is approximately 1 in 3,748,067. These are commonly compared to the chances of ridiculous occurrences, which often have a much higher chance of happening. Is it really a surprise that humans can be so easily attacked though? Sharks are apex predators that haven’t changed (much) in millions of years. They’re perfectly formed for aquatic hunting and many species have an inquisitive nature and explore new stimuli with their mouths – meanwhile humans are perfectly adapted to survive in multiple terrestrial environments.

Sharks are not the only creature that pose a threat to humans in the water. Stings are an issue for humans as well. Jellyfish (Medusozoa Cnidaria) are gelatinous animals that are, for the majority, directed around the ocean by currents due to their lack of muscle. It should be noted that “jellyfish” is a term being debated for accuracy, as they are invertebrates (spineless creatures), unlike fish which are vertebrates (creatures with a backbone), and actually have little in common with other fish species – the names “jellies” or “sea jellies” are becoming more frequently used. They hunt and defend themselves by the dangling tentacles that trail after them in their movement. These tentacles have a series of nematocysts (an explosive cell that fires a toxin-containing structure called a cnidocyst). It is these that sting humans and, in some cases, kill them. There are a few species of jellyfish that are especially dangerous to humans; Box Jellyfish (class: Cubozoa) and Irukandji Jellyfish can cause severe allergic reactions in humans. The Sea Wasp is a type of box jellyfish that can kill an adult human in minutes, and is known as the most dangerous jellyfish in the world after killing at least 63 people in Australia over a 12 year period.

In addition to jellyfish, there are other stinging animals that can injure and kill humans. Stingrays are a group of rays that are identified by the barbed stingers (that are modified forms of the scales that cover their bodies) which they use in self-defence. They are commonly found in coastal, tropical, and subtropical waters, with some species being found in warmer temperate oceans and the deep ocean. The previously mentioned stingers have two grooves with venom glands located along the underside, and they are protected by the integumentary sheath (a thin layer of skin that contains them). This form of defence is usually used against sharks, their natural predator, but when diving humans antagonise them or when humans in shallow water step on them, they are forced to respond with their stingers. The occurrence of this that gained the most media attention was that of celebrity conservationist Steve Irwin, who died because of a stinger strike that perforated his chest cavity resulting in his death.

The issue with water itself

But what about sources of danger that are not because of animal life? The water itself is equally as dangerous as the animals within it. Whirlpools have been discussed and feared for years, and are created when opposing currents meet. This creates a circular motion that can funnel down (termed a vortex), which is typically pictured in old books and paintings. A large, powerful whirlpool in an ocean is termed a maelstrom, usually formed by tides, which are the types known to occasionally sink ships. However, this is rare, and naturally forming whirlpools do not typically kill people. It is the man-made whirlpools that are most dangerous, and when one was created due to a 1980 drilling disaster, it dragged a drilling platform, eleven barges, trees, and land underneath the water. Once the pressure equalised, nine of the eleven barges reappeared on the surface of the lake, and if people were present many lives could have been lost.

A more frequent occurrence is that of rip currents. They are movements of water that occur near shores and are responsible for 46 deaths by drowning per year and the reason for the most lifeguard rescues at beaches. They are caused by the movement of water moving away from the shore. The tides and the wind pushes seawater up the shore, which then returns back to the water, through the path of least resistance. This creates an invisible “funnel” of water pushing back out to the open water at a right angle from the shore. This means that people can be pushed out to the deep without realising, stranding them at depth. Alternatively, they can realise they’re being pushed out, and swim against the current, which tires them to the point of drowning.

A popular whitewater rafting location in the French Alps (The river Guil). Image: Harry Wood, 2001. Wikipedia Commons.

In freshwater locations, a similar action can take place. A risk factor for people who enjoy white water rafting is the hydraulic action of water. Hydraulics or “holes” are created by water flowing from a high point (a ledge or a submerged object) which causes the surface water to flow backwards towards the object. This creates a circular movement of water that can drag people down into a spinning movement of water. In extreme circumstances, it can create a vortex powerful enough to drag a boat to the bottom of a deep ‘hole’. These hydraulics can also be man-made; weirs have a uniform structure as they’re typically so wide with blocking walls either side meaning there is no escape point if someone was dragged under. The method of escaping these hydraulic movements is highly debated, and no concrete method has been decided upon, with professional rafters losing their lives in them. The circular rotation of both water and occasionally people have proven to be even more dangerous when the factor of debris is considered. This rapid movement of water has been known to drag objects into the “hole” meaning there are obstructions to hit if someone or something were to be dragged under, creating the effect of a grinder.

Overall, humans have proven to be ill-prepared for a life in or near the water. We’re not prepared for the power of water, or the animals within it. We are much better suited for a life on the land, and rightly so. Human evolution has taken millions of years, and we are the most dominant animal on the planet as well as being massively widespread – we’re just not ready for surviving in the water.

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Extreme marine habitats is a site dedicated to those habitats that are simply extreme! Written by students, we aim to provide detailed and insightful information on a variety of marine science subjects.